Adaptive repetitive control of wrist tremor suppression based on functional electrical stimulation / 生物医学工程学杂志

Tremor is an involuntary and repetitive swinging movement of limb, which can be regarded as a periodic disturbance in tremor suppression system based on functional electrical stimulation (FES). Therefore, using repetitive controller to adjust the level and timing of FES applied to the corresponding muscles, so as to generate the muscle torque opposite to the tremor motion, is a feasible means of tremor suppression. At present, most repetitive control systems based on FES assume that tremor is a fixed single frequency signal, but in fact, tremor may be a multi-frequency signal and the tremor frequency also varies with time. In this paper, the tremor data of intention tremor patients are analyzed from the perspective of frequency, and an adaptive repetitive controller with internal model switching is proposed to suppress tremor signals with different frequencies. Simulation and experimental results show that the proposed adaptive repetitive controller based on parallel multiple internal models and series high-order internal model switching can suppress tremor by up to 84.98% on average, which is a significant improvement compared to the traditional single internal model repetitive controller and filter based feedback controller. Therefore, the adaptive repetitive control method based on FES proposed in this paper can effectively address the issue of wrist intention tremor in patients, and can offer valuable technical support for the rehabilitation of patients with subsequent motor dysfunction.

Core muscle functional strength training for reducing the risk of low back pain in military recruits: An open-label randomized controlled trial.

BACKGROUND: Core muscle functional strength training (CMFST) has been reported to reduce injuries to the lower extremity. However, no study has confirmed whether CMFST can reduce the risk of low back pain (LBP). OBJECTIVE: This study identified the effects of CMFST on the incidence of LBP in military recruits. DESIGN, SETTING, PARTICIPANTS AND INTERVENTION: We performed a prospective, open-label, randomized, controlled study in a population of young healthy male naval recruits from a Chinese basic combat training program. Participants were randomly assigned to either the core group or the control group. In additional to normal basic combat training, recruits in the core group underwent a CMFST program for 12 weeks, while recruits in the control group received no extra training. MAIN OUTCOME MEASURES: At the beginning of the study and at the 12th week, the number of participants with LBP was counted, and lumbar muscle endurance was measured. In addition, when participants complained of LBP, they were assessed using the visual analog scale (VAS) and Roland Morris Disability Questionnaire (RMDQ). RESULTS: A total of 588 participants were included in the final analysis (295 in the core group and 293 in the control group). The incidence of LBP in the control group was about twice that of the core group over the 12-week study (20.8% vs 10.8%, odds ratio: 2.161-2.159, P < 0.001). The core group had better lumbar muscle endurance at 12 weeks than the control group ([200.80 ± 92.98] s vs [147.00 ± 84.51] s, P < 0.01). There was no significant difference in VAS score between groups, but the core group had a significantly lower RMDQ score at week 12 than the control group (3.33 ± 0.58 vs 5.47 ± 4.41, P < 0.05). CONCLUSION: This study demonstrated that the CMFST effectively reduced the incidence of LBP, improved lumbar muscle endurance, and relieved the dysfunction of LBP during basic military training.

Core muscle functional strength training for reducing the risk of low back pain in military recruits: An open-label randomized controlled trial / 中西医结合学报

BACKGROUND@#Core muscle functional strength training (CMFST) has been reported to reduce injuries to the lower extremity. However, no study has confirmed whether CMFST can reduce the risk of low back pain (LBP).@*OBJECTIVE@#This study identified the effects of CMFST on the incidence of LBP in military recruits.@*DESIGN, SETTING, PARTICIPANTS AND INTERVENTION@#We performed a prospective, open-label, randomized, controlled study in a population of young healthy male naval recruits from a Chinese basic combat training program. Participants were randomly assigned to either the core group or the control group. In additional to normal basic combat training, recruits in the core group underwent a CMFST program for 12 weeks, while recruits in the control group received no extra training.@*MAIN OUTCOME MEASURES@#At the beginning of the study and at the 12th week, the number of participants with LBP was counted, and lumbar muscle endurance was measured. In addition, when participants complained of LBP, they were assessed using the visual analog scale (VAS) and Roland Morris Disability Questionnaire (RMDQ).@*RESULTS@#A total of 588 participants were included in the final analysis (295 in the core group and 293 in the control group). The incidence of LBP in the control group was about twice that of the core group over the 12-week study (20.8% vs 10.8%, odds ratio: 2.161-2.159, P < 0.001). The core group had better lumbar muscle endurance at 12 weeks than the control group ([200.80 ± 92.98] s vs [147.00 ± 84.51] s, P < 0.01). There was no significant difference in VAS score between groups, but the core group had a significantly lower RMDQ score at week 12 than the control group (3.33 ± 0.58 vs 5.47 ± 4.41, P < 0.05).@*CONCLUSION@#This study demonstrated that the CMFST effectively reduced the incidence of LBP, improved lumbar muscle endurance, and relieved the dysfunction of LBP during basic military training.

[A Detection Technique for Gas Concentration Based on the Spectral Line Shape Function].

The methods that can rapidly and precisely measure concentrations of various gases have extensive applications in the fields such as air quality analysis, environmental pollution detection, and so on. The gas detection method based on the tunable laser absorption spectroscopy is considered a promising technique. For the infrared spectrum detection techniques, the line shape function of an absorption spectrum of a gas is an important parameter in qualitative and quantitative analysis of a gas. Specifically, how to obtain the line shape function of an absorption spectrum of a gas quickly and accurately is a key problem in the gas detection fields. In this paper we analyzed several existing line shape functions and proposed a method to calculate precisely the line shape function of a gas, and investigated the relation between the gas concentration and the peak value of a line shape function. Then we experimentally measured the absorption spectra of an acetylene gas in the wavelength range of 1,515-1,545 nm with a tunable laser source and a built-in spectrometer. With Lambert-Beer law we calculated the peak values of the line shape function of the gas at the given frequencies, and obtained a fitting curve for the line shape function in the whole waveband by using a computer program. Comparing the measured results with the calculated results of the Voigt function, we found that there was a deviation-between the experimental results and the calculated results. And we found that the measured concentration of the acetylene gas by using the fitting curve of the line shape function was more accurate and compatible with the actual situation. Hence, the empirical formula for the line shape function obtained from the experimental results would be more suitable for the concentration measurement of a gas. As the fitting curve for the line shape function of the acetylene gas has been deduced from the experiment, the corresponding peak values of the spectral lines can be immediately calculated out from the curve and used for the measurements of different concentrations of acetylene gases. Therefore, the calculation for the line shape function values is greatly simplified. The obtained data of the line shape function of the acetylene gas can be used for remote sensing of the gas, and the proposed method can also be applied for the measurements of line shape functions of other gases.

[Gas Concentration Measurement Based on the Integral Value of Absorptance Spectrum].

The absorptance spectrum of a gas is the basis for the qualitative and quantitative analysis of the gas by the law of the Lambert-Beer. The integral value of the absorptance spectrum is an important parameter to describe the characteristics of the gas absorption. Based on the measured absorptance spectrum of a gas, we collected the required data from the database of HIT-RAN, and chose one of the spectral lines and calculated the integral value of the absorptance spectrum in the frequency domain, and then substituted the integral value into Lambert-Beer's law to obtain the concentration of the detected gas. By calculating the integral value of the absorptance spectrum we can avoid the more complicated calculation of the spectral line function and a series of standard gases for calibration, so the gas concentration measurement will be simpler and faster. We studied the changing trends of the integral values of the absorptance spectrums versus temperature. Since temperature variation would cause the corresponding variation in pressure, we studied the changing trends of the integral values of the absorptance spectrums versus both the pressure not changed with temperature and changed with the temperature variation. Based on the two cases, we found that the integral values of the absorptance spectrums both would firstly increase, then decrease, and finally stabilize with temperature increasing, but the ranges of specific changing trend were different in the two cases. In the experiments, we found that the relative errors of the integrated values of the absorptance spectrum were much higher than 1% and still increased with temperature when we only considered the change of temperature and completely ignored the pressure affected by the temperature variation, and the relative errors of the integrated values of the absorptance spectrum were almost constant at about only 1% when we considered that the pressure were affected by the temperature variation. As the integral value of the absorptance spectrum varied with temperature and the calculating error for the integral value fluctuates with ranges of temperature, in the gas measurement when we usd integral values of the absoptance spectrum, we should select a suitable temperature variation and obtain a more accurate measurement result.

Subtypes of breast cancer show different patterns of metastasis：a 10-year survival analysis of 390 patients with primary breast cancer / 中国癌症杂志

Background and purpose:Breast cancer can be divided into several molecular subtypes according to its biomarkers. The pattern of distant metastasis has a great clinic significance but was rarely investigated. This study investigated the impact of molecular subtype of breast cancer on initial sites of metastasis..Methods:All the patients with operable invasive breast cancer diagnosed in Zhongshan People’s Hospital between 1998 and 2004 were recruited. Subtypes were defined as Luminal A, Luminal B, human epidermal growth factor receptor 2 (HER-2) enriched, and triple negative (TN) according to the expression of estrogen receptor (ER), progestogen receptor (PR) and HER-2 status. The first distant metastatic sites and the time of their appearances were recorded. Survival curves were constructed using the Ka-plan-Meier technique.Results:Among 390 eligible patients, there were 215(55.1%) with Luminal A, 43 (11.0%) with Lu-minal B, 52 (13.3%) with HER-2 enriched, and 80 (20.5%) with TN. The median follow-up time was 118 months (11-163 months). Seventy-two (18.5%) distant metastases occurred during follow-up: 37 metastases in Luminal A, 8 in Luminal B, 10 in HER-2, 17 in TN. Bone was the most common site of the first distant metastasis (39/72, 54.2%) followed by lung (25/72, 34.7%), liver (22/72, 30.6%), and brain (7/72, 9.7%). Among all the metastases, tumors of Luminal type (Luminal A 70.2%, Luminal B 50.0%) had a higher chance of bone involvement than that of HER-2 enriched (30.0%) and TN (35.3%,P=0.03). Both Luminal B (37.5%) and TN (17.6%) subtypes had a higher percentage of brain involvement than Luminal A and HER-2 enriched (P=0.01). The survival analysis showed no significant difference among the four subtypes in 9-year distant metastasis-free survival. However, distant metastasis appeared earlier in HER-2 enriched and TN breast cancer than in Luminal type.Conclusion:Organ-specific metastasis may depend on the molecular subtype of breast cancer. Bone metastasis occurs more in luminal type than in other types. Luminal B and TN types of tumors had more chance of brain metastasis than Luminal A and HER-2 enriched type of tumors.

Clinical experience on postoperative balance of hemostasis and antithrombus for patients with hemophilic arthritis after arthroplasty / 中国骨伤

<p><b>OBJECTIVE</b>To observe the clinical significance of postoperative personalized antithrombotic therapy for patients with hemophilic arthritis (HA) patients after arthroplasty.</p><p><b>METHODS</b>From September 2005 to October 2013, 11 cases of arthroplasty for hemophilic arthritis in hip and knee total operation 14 times,including 1 case of double knees (calculated as one operation), operation in left knees 6 times, operation in right knees 5 times, 2 in hip. All the patients were male and the age ranged from 23 to 57 years old,with an average of (36.1 ± 11.0) years old; the average weight was (64.1 ± 8.9) kg. All the patients were preoperatively diagnosed and classified as hemophilic arthritis with the radiological images and laboratory tests. According to the function of joints, the risk of postoperative venous thromboembolism (VTE), and dynamic observation of Factor VIII:C (FVIII:C) activity, patients were treated with personalized antithrombus by adjusting the dosage of recombinant human coagulation factor VIII (Kogenate FS). All the patients were orderly divided into postoperatively distal joints moving group and none-moving group to observe the coagulation function.</p><p><b>RESULTS</b>The enrolled patients had no postoperative complication of VTE and pulmonary embolism (PE). The APTT and D-2 were different between two groups in the postoperative early stage. Length of hospital day was shorter in the moving group than none-moving group.</p><p><b>CONCLUSION</b>Because of the self-coagulation disorder, patients with HA tended to bleed. However it doesn't mean that there is no risk of postoperative thrombosis. Therefore,it's important to determine how to control the balance between postoperative antithrombus, hemostasis,and coagulation factor replacement therapy after arthroplasty for HA. Postoperative moving has proved helpful for HA, especially in reducing the risk of hemostasis and shortening the time in hospital.</p>

Short-term curative effects of Tantalum rod treatment in early avascular necrosis / 中国骨伤

<p><b>OBJECTIVE</b>To explore the recent clinical curative effect of Tantalum rod in treating the early avascular necrosis.</p><p><b>METHODS</b>From January 2008 to November 2008, the 25 patients (39 hips) with early avascular necrosis accepted tantalum rod placement and included 9 males (11 hips) and 16 females (28 hips) with an average age of 37 years old ranging from 18 to 74 years old. Four patients (6 hips) caused by Alcoholic, 6 patients (8 hips) by hormone, 2 cases (2 hips) by traumatic, 13 cases (23 hips) by idiopathic. Steinberg preoperative stage involved 7 hips in period I, 24 hips in period II, 8 hips in period III. Curative effect analysis included preoperative and postoperative Harris score, radiographic changes and hip replacement for follow-up to accept the end of the femoral head survival rate.</p><p><b>RESULTS</b>All patients were followed up for 6 to 47 months (averaged 37.4 months). All 12 hips imaging appeard progress,including tantalum rod exit in 1 hip, hip hemiarthroplasty collapse in 3 hips, the area increased to avascular necrosis in 8 hips. Six hips accepted total hip replacement, including imaging progress in 5 hips (41.7%, 5/12), no imaging progress in 1 hip (3.7%,1/27). All hips' Kaplan-Meier survival curves showed 6-month survival rate was (97.4 +/- 2.5)% after tantalum stick insertion, 1-year survival rate was (94.7 +/- 3.6), and 2-year survival rate was (88.6 +/- 5.4)%, 3-year survival rate was (72.5 +/- 11.2).</p><p><b>CONCLUSION</b>It is effective for treatment of avascular necrosis of femoral head in Steinberg I and II by Tantalum rod, and it can effectively relieve femoral head replacement time.</p>

Development and mechanical testing on TC hemi-arthroplasty prosthesis system for femoral intertrochanteric fractures / 医用生物力学

Objective To develop a new hemi-arthroplasty system-Trochanteric Prosthesis System (TC) for the treatment of unstable femoral intertrochanteric fractures in the elderly, so as to preserve bone mass and meet requirement of functional exercises at early stage. Methods A normal male adult volunteer was chosen to receive CT scanning at middle and upper regions of his both intact femur. The serial digitized image data of spiral CT in DICOM format were imported to finite element modeling software to establish a three-dimensional (3D) solid model of the proximal femur. The Pro/E software was used to conduct computer-aided design of the new hemi-arthroplasty prosthesis system and then its metal model was also made by rapid prototyping techniques. After repeated verification and improvement on cadaver femur, the femoral prosthesis was molded and assembled in the solid fracture mode for finite element analysis. The unstable femoral intertrochanteric fracture model obtained from the fresh cadaver of an elderly male was chosen to make A2.2 Type of such fracture model in AO classification system. The new hemi arthroplasty prosthesis system was implanted and assembled into the model and received mechanical testing, including material performance testing, prosthesis head/neck and stem fatigue testing, anti-compression and anti-torsion testing, according to the National Industrial Standard YY0117 and YY0118. Results The sample of new hemi-arthroplasty prosthesis sustained 5 million cycle (8 Hz) fatigue testing on the part of the head-neck and the stem body without any breakage and failure. With the sample implanted into the intertrochanteric fracture model, the maximum compressive strength and torsional strength of the sample reached over 2 kN and 15.5 N•m without failure, respectively. The contact stresses between the stem and the femur were mostly distributed at the region below the femoral trochanter, where the maximum average Von Mises stress values were 17.6~26.4 MPa. Stresses at the region of intertrochanteric fractures were at a low level. The maximum average Von Mises stress values at the greater and lesser trochanter region were 2.7 and 4.9 MPa, respectively. Conclusions The new developed hemi-arthroplasty prosthesis has the advantages of easy performance, reliable fixation, sufficient bone preservation and it is capable of fulfilling the demands of early weight bearing and functional exercises. It is suitable for the treatment of unstable femoral intertrochanteric fractures in the elderly.

Finite element analysis on stress distributions during novel semi-hip prosthesis assembly / 医用生物力学

Objective To simulate the stress generated by contact with the femur during the assembly of novel semi-hip prosthesis, and discuss the operating limits and adaptive prosthesis profile in clinic. Methods CT scans were conducted on the proximal end of the femur in a male volunteer of 60 years old as a physical model. By transferring the CT data to finite element modeling software, the physical model was simplified, meshed, materialized and assembled with the model of prosthesis to establish the three-dimensional finite element model. Surface to surface contact relationship between the femur and the prosthesis was also constructed by utilizing contact elements. Relative sliding distance and stress distribution were solved while simulating the process of assembling the prosthesis. Results Additional stress was generated on the sudden change area of the contact surface when the prosthesis was seated. The greatest contact pressure came from the changing section of the ridge of the prothesis, and the maximum assembly stress and sliding distance range increased nonlinearly along with the pushing distance. The increase rate of additional stress was enhanced significantly while Δz≥0.5 mm. Conclusions Compared with the prosthesis without ridge, the prosthesis with ridge can be easily seated and obtain mechanical stabilization. However, the relevant clinical operating limits should be obeyed to avoid generating excessive additional stress during the implantation of prosthesis, which may cause treatment failure due to the damage in bone cortex.

Effect of poly (ethylene glycol) on coarsening dynamics of titanium dioxide nanocrystallites in hydrothermal reaction and the application in dye sensitized solar cells.

Titanium dioxide sols were synthesized by hydrothermal reactions with addition of poly (ethylene glycol) (Mw=20,000). Using techniques of X-ray diffraction, transmission electron microscopy, dynamic light scattering, and scanning electron microscopy, effect of PEG on the crystallographic properties, particle size, aggregating behavior, and the morphological properties of nanoparticles in the sols were studied. It was found that growth of anatase nanocrystallites was retarded by PEG. Average crystallite size of anatase nanocrystallites first decreased from 20.7 nm to 10.5 nm as the polymer concentration increased from 1 g/L to 3 g/L, and then changed little. Meanwhile, small amount of rutile phases like rutile nanowires, twin crystallites, and the "flowers" appeared continuously when the concentration increased from 3 g/L to 5 g/L. Mono-dispersion was obtained with relatively lower PEG concentration. The observed evolvement was discussed based on the interaction between the polymers and the nanocrystallites with assistance of FTIR. The coverage of polymer chains on surface of nanocrystallites leads to isolated reactors, which benefits the uniform coarsening rate of the nanocrystallites. The synthesized TiO(2) sols were utilized in dye sensitized solar cells. Performance parameters of the solar cells were discussed with assistance of dye desorption experiments. The improved dispersion in sols was found to benefit the photovoltaic performance of the cells.

Optically-induced-potential-based image encryption.

We present a technique of nonlinear image encryption by use of virtual optics. The image to be encrypted is superposed on a random intensity image. And this superposed image propagates through a nonlinear medium and a 4-f system with single phase key. The image is encrypted to a stationary white noise. The decryption process is sensitive to the parameters of the encryption system and the phase key in 4-f system. This sensitivity makes attackers hard to access the phase key. In nonlinear medium, optically-induced potentials, which depend on intensity of optical wave, make the superposition principle frustrated. This nonlinearity based on optically induced potentials highly improves the secrecy level of image encryption. Resistance against attacks based on the phase retrieval technique proves that it has the high secrecy level. This nonlinear image encryption based on optically induced potentials is proposed and demonstrated for the first time.

Fraunhofer computer-generated hologram for diffused 3D scene in Fresnel region.

A Fraunhofer computer-generated hologram (CGH) is proved to be valid in display for three-dimensional (3D) objects from the Fresnel to the far-field region without a Fourier lens for reconstruction. To quickly compute large and complicated 3D objects that consist of slanted diffused surfaces in the Fresnel region, a Fraunhofer-based analytical approach using a basic-triangle tiling diffuser is developed. Both theoretical and experimental results reveal that Fraunhofer CGH can perform the same effects as Fresnel CGH but require less calculation time. Impressive 3D solid effects are achieved in the Fresnel region.

Three-dimensional imaging with monocular cues using holographic stereography.

Two quantitative criteria are derived to evaluate monocular cues in holographic stereograms. We find that the reconstruction has correct monocular cues when the whole scene is located in a so-called "monocular cues area" with compatible monocular and binocular cues. In contrast, incorrect monocular cues appear when the scene is in the other two areas, namely, the "visible multi-imaging area" and the "lacking information area." A pupil-function integral imaging algorithm is developed to simulate monocular observation, and a holographic printing system is set up to fabricate full-parallax holographic stereograms. Both simulations and experiments agree with the criteria.

High-speed full analytical holographic computations for true-life scenes.

We develop a novel method to generate hologram of three-dimensional (3D) textured triangle-mesh-model that is reconstructed from ordinary digital photos. This method allows analytically encoding the 3D model consisting of triangles. In contrast to other polygon based holographic computations, our full analytical method will free oneself from the numerical error that is in the angular spectrum due to the Whittaker-Shannon sampling. In order to saving the computation time, we employ the GPU platform that is remarkably superior to the CPU's. We have rendered a true-life scene with colored textures as the first demo by our homemade software. The holographic reconstructed scene possesses high performances in many aspects such as depth cues, surface textures, shadings, and occlusions, etc. The GPU's algorithm performs hundreds of times faster than those of CPU.

Total hip arthroplasty for the post-traumatic osteoarthritis after open reduction and internal fixation of acetabular fracture / 中华外科杂志

<p><b>OBJECTIVE</b>To explore the surgical strategy of traumatic osteoarthritis of the hip joint secondary to the failure of open reduction and internal fixation (ORIF) treatment on acetabular fractures.</p><p><b>METHODS</b>Eighteen cases of traumatic osteoarthritis of the hip joint received total hip arthroplasties from May 2002 to December 2009, who had undergone the surgery of ORIF after acetabular fractures. There were 12 male and 6 female with an average age of 53 years (45 to 66 years). It was average 11.2 months (6.0 to 24.0 months) from the present of pain and limp to the operation. It was average 35 months (8 to 72 months) from ORIF procedure on acetabular fracture to total hip arthroplasty. Harris score was 50 points in average (26 to 70 points).</p><p><b>RESULTS</b>All 18 cases were followed up 40 months in average (12 to 86 months). They were allowed to get out of bed on 1 week after the operation. The time of full weight bearing lagged to 2 or 3 months after the operation. All patients had the function of their hips improved with Harris score of 86 points in average (80 to 92 points).</p><p><b>CONCLUSIONS</b>The procedures of ORIF on acetabular fracture make lots of trouble to total hip arthroplasty. It is important to rebuild the normal biological mechanisms of acetabulum and uses uncement fixed prosthesis as possible as it can.</p>

[Influence of nitrogen doping on electron structure and optical properties of amorphous carbon thin films].

Nitrogen doped amorphous carbon (a-C : N) thin films were prepared by DC magnetron sputtering. The films were investigated by AES, UV-Vis and ellipsometer. A parameter 'D' defined as the distance between the maximum of positive going excursion and the minimum of negative going excursion was calculated in the derivative AES spectra. The values of 'D' were used to calculate the percentage of sp2 hybrid bonds. The optical transmission and the optical band gap of the films were characterized by an UV-Vis spectrophotometer. The results showed that the optical band gap decreased and then increased with the increase of N2 gas source. The transmission and refractive index changed in reverse order. It was demonstrated that the thin film with low percentage of nitrogen was beneficial to the formation of sp3 hybrid bonds and caused the optical band gap of the thin film to increase. As a result, the thin film should be prepared under low percentage of nitrogen pressure to ensure that it possesses fine optical properties.

The use of a closed-suction drain in total knee arthroplasty: a prospective, randomized study / 中华外科杂志

<p><b>OBJECTIVE</b>To determine the value of using a closed-suction drain in cemented knee arthroplasty.</p><p><b>METHODS</b>One hundred patients were prospectively randomized into two groups, one group underwent cemented total knee replacement with a single deep closed-suction drain, and the other group (n = 50) no drain.</p><p><b>RESULTS</b>The total blood loss was significantly greater in those with a drain although those without lost more blood into the dressings. There was no statistical difference in the postoperative swelling or pain score, ecchymosis, deep vein thromboses (DVT), time at which flexion was regained or the incidence of infection at a minimum of two years after surgery in the two groups.</p><p><b>CONCLUSION</b>There is no evidence to support the use of a closed-suction drain in cemented knee arthroplasty.</p>

The effect of rotational alignment of the femoral components on the patellofemoral biomechanics in total knee arthroplasty / 中华外科杂志

<p><b>OBJECTIVE</b>To study the effect of rotational alignment of the femoral components on the patellofemoral biomechanics in total knee arthroplasty (TKA) demonstrated on autopsy specimens, as the guide for surgeons to choose the correct reference axis for rotational alignment of the femoral components and to reduce the patellofemoral joint complications.</p><p><b>METHODS</b>Select 9 frozen fresh human cadaver knees without gross deformities or instabilities and mount specimens on a patellofemoral joint testing jig connected to a Model 8501 Instron machine (Instron Corporation, Canton, MA). The study simulated the action of squatting from the standing position with the foot firmly planted. Standard TKA was performed in each specimen by the same senior surgeon using Nexgen LPS total knee system (Zimmer Corporation, Warsaw Indiana). Alter rotational alignment of the femoral components referenced to the transepicondylar axis and the Whiteside's line respectively. Measure biomechanics of the patellofemoral joints using Fuji prescale film at 30 degrees , 60 degrees , 90 degrees , 120 degrees of knee flexion respectively. The digital values were obtained by the handheld pressure measurement systems (FPD-305E, FPD-306E) and Autocad software.</p><p><b>RESULTS</b>The rotational alignment of the femoral components paralleled to the transepicondylar axis had the best results of the peak value of the patellofemoral contact pressure (P < 0.05). There were no statistically significant differences in patellofemoral contact area (P > 0.05). But the patellofemoral contact area had the close correlations to the angles of the knee flexion and the specimens.</p><p><b>CONCLUSIONS</b>Rotational alignment of the femoral components has a great influence on the patellofemoral contact pressure in total knee arthroplasty. It is reliable for surgeons to choose the transepicondylar axis as the reference axis to rotate femoral components.</p>

Radiographic analysis of rotational malalignment between tibial component and femoral component in total knee arthroplasty / 中华外科杂志

<p><b>OBJECTIVE</b>To identify possible reasons of rotational mismatch between tibial component and femoral component in total knee arthroplasty and choose a right reference axis for placing the components in the operation and to decrease the complications.</p><p><b>METHODS</b>Forty normal Chinese knees were studied. There were 20 men and 20 women, and average age was 34 years (range, 18 - 42 years). The images of cross sections of the distal femur were obtained by spiral CT scanning (0.5 mm thickness). Scan direction was aligned to be in the plane perpendicular to the mechanical axis of the tibia. On the images of the distal femur and the proximal tibia, three baselines for the anteroposterior axis of the femoral component were drawn based on the clinical epicondylar axis and the surgical epicondylar axis and 3 degrees lateral rotated to the posterior condylar surfaces of the femur separately, and a baseline for the anteroposterior axis of the tibial component was drawn based on the medial 1/3 of the tibial tuberosity. The rotational mismatch angles were measured between each component by using the Autocad software.</p><p><b>RESULTS</b>The mean rotational mismatch angle between tibial component and femoral component is 2.94 degrees for the clinical epicondylar axis, 6.50 degrees for the surgical epicondylar axis and 6.83 degrees for 3 degrees lateral rotation of the femoral component referenced to the posterior condylar axis separately.</p><p><b>CONCLUSIONS</b>Landmarks of each bone were the intrinsic cause of the rotational mismatch in total knee arthroplasty. The clinical epicondylar axis can be chosen for the ideal reference to rotational alignment of the femoral component because of its minimal rotational mismatch between each component.</p>